I hope this won't be interpreted as advertising. I make this post to simply support my statement about all the activity in the subwoofer world.
Here is an upcoming subwoofer from another company. Look at the size of this beast - 23 3/8" wide x 25" tall x 30" deep - around 200 lbs.
It has what I consider to be a rather unique design - an internally mounted 15" active driver (inside the box, you can see the baffle that will hold this driver), and 3 18" passive radiating drivers, one on each side and one in the front. The square opening in the back is for the amplifier.